Spina bifida is a relatively common, structural malformation that is associated with excess morbidity and mortality. A specific etiologic agent(s) cannot be identified in the majority of individuals with spina bifida, and in this group of patients the condition is believed to be a genetically complex trait. As with other complex human traits, spina bifida is thought to be influenced by common genetic variants that, individually, may have only a small to moderate effect on risk. Our funded study is designed to address the hypothesis that common variants in folate-related genes contribute to the risk of spina bifida. Our evaluation of this hypothesis considers the roles played by both the maternal and embryonic genotype, and the possibility that the interplay of genes and environmental risk factors may be more relevant to the risk of spina bifida than is the independent main effect of any one susceptibility locus. In this investigator-initiated, revision application, we propose to: (1) change the method used for the collection of samples for DNA extraction (from buccal brushes to saliva) for newly enrolled subjects, and (2) add the collection of a saliva sample from enrolled study subjects who previously provided a buccal brush sample. These revisions will enhance our ability to achieve the immediate and long- term goals of our research program, by providing an improved source of DNA (relative to buccal brushes) for our current and future investigations. Specifically, improvement in DNA quality will result in decreased measurement error (i.e. decreased genotyping errors, which can lead to differential bias in family-based studies) and improved genotyping call rates (i.e. less missing data), which will have a positive impact on the validity and precision of our study findings. Further, improved DNA yield will allow us to take advantage of high-density genotyping platforms, which offer both cost and time efficiency, and will enhance the long-term, scientific usefulness of our DNA bank. PUBLIC HEALTH RELEVANCE: Neural tube defects, including spina bifida, are common, serious birth defect that affects approximately 324,000 births worldwide (1) and 3,000 pregnancies in the United States annually. Our funded study will provide important information regarding the factors that influence the risk of spina bifida that, ultimately, will allow for more accurate genetic counseling and improved methods for preventing this condition. The proposed revisions to the funded study, which are aimed at increasing the quantity and quality of the DNA available for our investigations, will improve the likelihood that the study goals will be realized. [unreadable] [unreadable] [unreadable]